ORTMANN: FAMILIES AND GENERA OF NAJADES. 321 
marsupium in this genus is not very peculiar, though assuming the 
characteristic kidney-shape of the higher Lampsiling. The task of 
aérating the glochidia is taken up by the edge of the mantle in front 
of the branchial opening. However, the latter is as yet very little 
differentiated morphologically, but the thickened (muscular) margin 
and the pigment indicate that it actually has a special function. The 
shell of Obovaria presents no remarkable features, though it is possibly 
archaic, for it reminds of certain forms of Fusconaja and Quadrula. 
This genus is divided by Simpson into two subgenera, which are 
very well defined. 
Subgenus Obovaria (sens. strict.). 
Shell rounded, rather upright, beaks more or less in the middle of the 
upper margin. Pseudocardinals normal and divergent. 
Type O. retusa (Lamarck). 
Subgenus Pseudodn Simpson (1900), p. 601). 
Shell ovate, oblique, beaks quite anterior. Pseudocardinals (at 
least in old shells) oblique, almost parallel to the laterals. 
Type O. ellipsis (Lea). 
At first glance, O. ellipsis looks very different from typical Obovaria, 
and I was for some time inclined to unite it with Nephronajas; but 
O. castanea clearly forms a connection with the typical forms. 
Simpson (/. c.) describes the soft parts of Pseudoén, and says: 
“mantle having a wide, thickened, double border, the inner edge being 
toothed throughout below.’’ This is incorrect. The inner edge is 
slightly widened and crenulated only for a short distance in front of 
the branchial: Simpson also says that the ovisacs are ‘‘tinted with 
purple below.”’ I have not seen this in O. castanea, although O. 
ellipsis hasa slight purplish gray pigment at the edge of the marsupium:; 
but this should not be described as “‘ purple.” 
Obovaria retusa (Lamarck). 
On August 29, 1908, I found a gravid female with eggs in the Ohio 
River in Beaver Co., Pennsylvania, and on September 22, 1910, I 
secured two males and two gravid females, with glochidia, in the 
Ohio River at Portland, Meigs Co., Ohio. 
The soft parts have been described by Lea (Obs., X, 1863, p. 433). 
Anal and supra-anal separated by a short mantJe-connection. Anal 
crenulated, branchial with papilla. In front of the branchial the inner 
edge of the mantle in the female is slightly dilated and lamelliform, 
